1. Field of the Invention
The present invention relates to a cleaning solution and a method of cleaning an anti-reflective coating (ARC) composition using the same and, more particularly, to a method of cleaning accumulated and cured ARC compositions remaining on semiconductor manufacturing equipment.
2. Description of the Related Arts
Recently, as digital information has become more widely adopted, the use of computers has become widely spread. With increasing amounts of digital information becoming available and with the growing need to process greater amounts of digital information, there is an ever-growing demand and requirement placed on semiconductor devices for faster operating speeds as well as for handing and processing greater amounts of digital data. In order to satisfy these requirements, manufacturing methods for semiconductor devices have been developed to increase the degree of integration, increase reliability and increase processing and response time. In order to increase the degree of integration in semiconductor devices, efforts have been and are being made towards reducing the cell size and margin of all of the patterns formed on a semiconductor substrate. On the other hand, a vertical size of semiconductor devices, that is, an aspect ratio of each element making up the semiconductor device, has increased.
Current day semiconductor devices generally include a transistor structure with appropriate doping regions, a capacitor, and an electrical interconnection pattern to connect these various components. The manufacture of current day semiconductor devices requires a multitude of process steps, including photolithography, doping, etching and thin film deposition. Among these process steps, one of the most important areas of semiconductor manufacturing process that has enabled high levels of semiconductor device integration is photolithography.
Photolithography is a basic process that is essential to current day semiconductor fabrication. Every semiconductor device requires at least several photolithography processes to form desired circuit patterns as mandated by its design. As the design of semiconductor devices dictate higher levels of integration, the role of photolithography becomes more important.
Photolithography may be used for patterning a semiconductor substrate, a metal layer, an insulating layer, etc. in the manufacture of an integrated circuit of a semiconductor device. Although the technical details of how photolithography is carried out are complex, the theory of photolithography is relatively easy to describe.
In order to form a pattern using photolithography, a photoresist film or layer is formed on a device wafer surface to be patterned, such as on an insulating layer or a conductive layer on a substrate. The photoresist film or layer may be made of an organic compound, the solubility of which to an alkaline solution changes after exposure to a light source, e.g., ultraviolet (UV) light or an X-ray. The photoresist film or layer is exposed by a light source through a photomask having a pattern to be transferred onto the device wafer surface. The photoresist film is then developed to remove those portions of the photoresist film having a high solubility (i.e., exposed portions for a positive type photoresist), while remaining portions having a low solubility (i.e., unexposed portions for a positive type photoresist) form a photoresist pattern. Layers underlying the photoresist pattern are then etched using the photoresist pattern as an etching mask, and thereafter the photoresist pattern may be removed to obtain a pattern used in forming conductive patterns, wiring, electrodes, as well as other components of a semiconductor device. However, as the level of integration increases and the size of devices become smaller, the photoresist compound used for the photolithography process poses various problems. One of these problems relates to diffused reflection during exposure of a photoresist layer. To address this problem, an organic anti-reflecting coating (“ARC”) process has been employed to minimize diffused reflection.
As described above, photolithography is used to form a pattern of an underlying layer using a photoresist onto which an optical phase can be formed. The optical phase corresponds to a transferring pattern to be formed on the underlying layer. After exposure and development of the photoresist film, the photoresist pattern is formed. However, as the size of semiconductor devices become smaller, e.g., to the degree of 0.35 microns or less, the wavelength of the light used for the exposure becomes shorter. Accordingly, the degree of reflection and scattering of light at the underlying layer increases with undesired exposure characteristics. For example, the undesired exposure might change the channel depth (CD) of small size devices.
In order to address the above-described problem, an ARC layer is formed between the photoresist film and the underlying layer. The thickness of the ARC layer is formed to be about 1000 Å or less. Accordingly, the ARC layer is very thin when compared with that of the photoresist film. In order to pattern the underlying layer after developing the photoresist film, the exposed ARC layer also should be removed.
The ARC layer is generally formed from a composition including a polyimide-based compound, a polyacrylate-based compound, and other like compounds. The thickness of the ARC layer is a function of its refractive index; however, the ARC layer is generally formed to a thickness between about 400–600 Å. The function of the ARC layer is to reduce a refractive coefficient of the exposure light during photolithography to reduce undesired exposure characteristics at the underlying layer due to reflection of the exposure light.
FIG. 1 is a cross-sectional, schematic view of an equipment for coating a photoresist or an organic ARC composition on a semiconductor wafer.
The equipment includes an outer container 10 having a cover at the upper portion thereof, and an inner container 60 containing a spin chuck 20 for supporting a wafer W. The spin chuck 20 is operatively coupled to a drive 30 through a bottom portion of the outer container 10 to rotate the wafer W which is fixed at the upper portion of the spin chuck 20.
The outer container 10 may have the same configuration as the inner container 60. The upper portion of the outer container 10 is maintained at a predetermined distance from the spin chuck 20 in order to prevent spattering of an organic material such as a photoresist material to the outer portion of the outer container 10 during a coating process of the organic material. A nozzle 40 for coating an organic material and a side rinse nozzle 50 are provided at the upper portion of the outer container 10. The nozzles 40 and 50 are movable towards and away from the plane of the wafer W.
The inner container 60 is installed at the inner portion of the outer container 10 to prevent spattering of organic materials such as photoresist compounds to the outer container 10. The inner container 60 is manufactured using a material having heat-resistance, scratch-resistance and low viscous properties. That is, the inner container 60 is comprised of TEFLON, PP (polypropylene), etc. The inner container 60 is periodically detached for a cleaning.
The wafer W positioned on the spin chuck 20 is fixed by vacuum through the spin chuck 20. The nozzle for coating organic material 40 moves downwardly and closer to the wafer W, and then the organic material is coated on the wafer W. At the same time, the spin chuck 20 driven by a driver 30 rotates at a constant velocity and the organic material coated on the surface of the wafer spreads out uniformly by a centrifugal force.
A rinsing solution supplied from the side rinse nozzle 50 removes organic material fixed at the edge portion of the wafer. After completing the rinsing operation, the rinsing solution is exhausted out through an exhausting pipe 70 provided through a bottom portion of the inner container 60. After completing the coating of the wafer with the organic material, the nozzle 40 for coating organic material and the side rinse nozzle 50 are moved upwardly, and the rotation of the spin chuck 20 stops. Then, the wafer coated with the organic material is transferred for implementing the next process.
The ARC layer formed on the wafer for the manufacture of a semiconductor device can be removed through an ashing process by using an ARC removing etching solution or plasma; however, the organic ARC adheres and cures on the inner container, and cannot be removed by the above methods. The inner container 60 is detached periodically and the fixed organic materials on the surface of the inner container are removed by a scratching method. This method requires a long time and reduces manufacturing productivity.
Accordingly, the viscosity of the ARC composition or the photoresist is controlled to an appropriate degree so that the coated composition on the wafer does not overflow the wafer. In addition, the rotational velocity also is controlled to an appropriate degree. However, the spattering of the organic material during implementation of the process is inevitable.
At this time, the cured organic ARC composition is hardened more than the photoresist and is difficult to remove. The cured organic ARC composition contaminates the equipment for implementing the photolithography process and causes various problems.
The above-described problems may be resolved by rinsing the inner container soon after applying the photoresist or organic ARC composition and by advantageously removing the organic materials. However, stopping the operation of the equipment for cleaning results in a reduction in production yield and is practically impossible. Accordingly, the photoresist or organic ARC composition that is overflowed or spattered on the equipment during the operation of the equipment is allowed to remain as it stands, and removal effort is implemented only once every one or two weeks. The organic material adhering on the equipment may become harder after a long lapse of time, and the removal thereof becomes all the more difficult.
Generally, the photoresist is easier to remove than the organic ARC. Some methods generally employed for the removal of these cured organic materials are as follows. First, the photoresist and the ARC may be removed by physically scratching the cured organic materials with a plastic bar. Second, the photoresist may be chemically removed, and the ARC may be removed through the scratching. Otherwise, the equipment is replaced with a new replacement. All of these methods, however, have negative and deleterious consequences on the manufacturing process of semiconductor devices. For example, the amount of time that is required to clean a single equipment is about 30 minutes, and this lost time has the effect of reducing not only the equipment cleaning efficiency but the overall manufacturing efficiency as well. Moreover, contaminant particles generated by physical abrasion and scratching during the cleaning requires proper elimination and disposal.
Proper cleaning and removal of contaminant materials from equipment is required for conducting semiconductor processes. While various methods are in practice, there is still a need for improved methods that reduce cleaning time without the negative consequences and impact to the manufacturing process.